Tuned oscillator circuit



TUNED OSC ILLATOR C IRCUIT Filed Sept. 29, 1954 INVENTOR dJ. 7/10 P 0N BY W ma,

ATTORNEY Patented Jan. 11, 1938 TUNED OSCLLATOR UIRCUET `Browder J. Thompson, Summit, N. J., assigner to Radio Corporation of America, a corporation of Delaware Application September 29, 1934, Serial No. 746,124

12 Claims.

This invention relates uo a new form of short wave tuned oscillatory circuit which is characterized by extremely low loss.

The customary tuned circuits used on wave 5 lengths of several meters and less comprise parallel or concentric lines having distributed constants, and small circuits having lumped inductance and capacitance. Of these, only the concen- Y tric lines give high impedance, since the radiation,

lll eddy current, and stray dielectric losses of the other circuits are usually high. Concentric. lines have the disadvantage of requiring a conductor at least one-quarter o1" a wave length long.

It has been proposed to provide a tuned circuit 1*" consisting oi two copper hemispheres supported on a copper rod with flanges on the hemispheres forming a timing capacity, while the supporting rod forms the inductance. Such an arrangement, however, introduces considerable loss in the circo cuit, because of the high external electrostatic eld set up. For the same reason, the tuning is affected by stray capacitances.

The present invention provides a highly elcient tuned oscillatory circuit having lsubstantially no external magnetic or electric iielcl, and this is achieved by the use of inner and outer conductors, the surface ci the outer conductor being substantially continuous electrically so that there is no external magnetic or electric eld, and the inner conductor being connected to the external elements ci the circuit by means of one or more leads extending through the outer conductor. Although it is appreciated that there are some losses produced by the connecting leads, the losses consist principally of resistance losses of the inner conductors and can be made to be very low. One advantage of the present invention lies in the substantial freedom of the circuit from the effects oi stray tuning due to movements of dielectrics and conductors near the surface.

The invention is described in more detail in connection with the accompanying drawing, wherein Figs. 1-3 illustrate different preferred embodiments of the invention.

Fig. l shows a cross section of a tuning circuit comprising a continuous hollow sphere I, preferably copper, enclosing tworods 2, 3 with the inner ends terminating in discs ll, 5 in the center to form a tuning capacity, the length of rod between discs 4, 5 and the surface of sphere l serving as the tuning inductance. Leads 6 are brought out of the tuning circuit through holes in the sphere. These leads can be tapped oil anywhere along the rods to match any external impedance.

Fig. 2 shows another embodiment which comprises a metallic cylinder l, preferably copper or brass, enclosing copper rods 8, 9 terminating in discs ll, 5 to form the inductance and capacitance respectively, as in Fig. l. Rod 8 is herein shown threaded at the end to permit variation in the capacity between the discs d, 5, merely by a turn of the tuning knob I. This arrangement is simpler to construct than the spherical arrangement of Fig. l, and possesses all of the advantages oi the latter.

in Fig. 3 is shown an arrangement which, in effect, is one-half oi that of Fig. 2, with the lead l brought out from the end of the support rod E2. The plate i3 at the free end of the rod l2 provides one terminal oi a capacitance whose other terminal is the outer surface oi the cylinder. The value of this capacitance may be adjusted by varying the length of rod l2. This embodiment has a considerable advantage in mounting, as the circuit can be placed directly on the ground plate of the apparatus.

Water cooling of the inner conductor l2 may be provided, if desired, by making the conductor hollow and causing a iiow of cooling iiuid through it by means oi an internal tube. Since, at high frequencies, the skin effect causes practically all the current to flow near the surface of the conductor, it will be readily understood that the resistance would not be appreciably increased by removing material from the interior of the conductor. For

the same reason, very little loss is introduced by the cooling fluid. If mercury is employed for the cooling, little or no loss will be introduced due to it comparatively low resistance.

Another advantage of the present invention, besides that or very low loss, is that the improved oscillatory circuits enable tuned circuits to be constructed for very short wave lengths of the order of one meter and less, while still providing appreciable lumped capacity, since the inductance can be made very low.

Although the arrangements illustrated in the drawing are preferred and have been shown to be symmetrical, it should be understood that the enclosing surface need not have any symmetrical shape or be a surface of revolution in order to practice the invention; nor is it necessary that the inner conductors be axially located or the condenser be substantially in the center.

of symmetry o1", or small openings in, the outer surface have no serious adverse eiect, and, electrically, are not greatly inferior to any ci the idealized structures illustrated. The essential thing is that the outer surface be substantially Lack continuous electrically, so that there is no externalrmagnetic or electric field.

What is claimed is:

n l. An ultra high frequency tuned Voscillatory circuit comprising a container in the form of a metallic surface of revolution, a lumped capacitor substantially in the center of said surface of revolution, and connected to said surface by inductance in the form'of support rods, and a lead within said'surface of revolution connected to the outer'surface of each of said support rods between the ends thereof and extending therefrom externally of and through said surface of revolution, said leads being physically separated from each other.

2. An 'ultra high frequency oscillatory circuit i comprising a substantiallyrenclosed metallic surfaceV of revolution, a capacitor comprising two separated plates substantially in the center of. said enclosed surface of revolution, a metallic'` supporting rod devoid of concentrated reactance directly connecting each of said plates to said surface, said rods forming an inductance which, taken together with the plates of said capacitor, comprise the oscillator circuit, the adjacent ends of said rods being separated substantially by the distance between said plates, and leads coupled to the outer surface of said rods and extending substantially perpendicular thereto and through said surface of revolution.

3. A high frequency tuned oscillatory circuit in accordance with claim 2, characterized in this that said enclosed surface of revolution is'V a sphere.

4. An ultra high frequency oscillatory circuit comprising a substantially enclosed cylinder, a capacitor comprising two separated plates substantially in the center of said enclosed cylinder, a metallic supporting rod devoid of concentrated reactance directly connecting each of said plates to a wall of said enclosure, said rods forming an ductance which, taken together with the plates of said capa itor, comprise the oscillatory circuit, the adjacen ends of said rods being separated substantially by the distance between said plates, and leads coupled to said rods and extending substantially perpendicular thereto and through said cylinder.

5. An ultra high frequency oscillatory circuit comprising a substantially enclosed metallic surface of revolution, a capacitor comprisingrtwo plates substantially in the center of said enclosed surface of revolution, a metallic supportingV rod for each plate of said capacitor connecting the plate to the surface, said rods forming an inductance which, taken togetl'ierwith the plates of said capacitor comprise the oscillatory circuit, means located externally of said surface for adjusting one of said support rods with respect to the other, for Varying the capacity betweenr said plates, and leads coupled to said rods and extending substantially perpendicular thereto and through said surface of revolution.

6. An ultra high frequency tuned'oscillatory circuit comprising a container in the form of a metallic surface of revolution, a lumped capacitor substantially in the center of said surface of revolution and connected to said surface by'inductance'in the form of sup-port rods, and leads extending from said support rods externally1 of said surface of revolution, said leads being adjustable over the lengths of said rods.

7. A high frequency tuned oscillatory circuit comprising a substantially continuous metallic surface enclosing an inductance in the form of two metallic rods and a capacitor in the form of a pair of separated metallic plates, one end of each rod electrically terminating at one of the plates and the other end at the enclosing surface, and means for adjusting the length of one of the rods within saidv surface for varying the distance between said plates, and a'lead connected to the outer surface of each of said support rods and extending externally of and through said surface:

8. An ultra-high frequency tuned oscillatory circuit comprising a container in the form of a substantially continuous metallic surface, a lumped' capacitor substantially inthe center of said surface and connected to said'surface by inductances in the form of Vsupport rods, and a lead' within said container connected to the outer surface of each of said support rods between the ends thereof and extending therefrom externally of and through said container, said leads being physically Vseparated from each other.

9. A high frequency tuned oscillatory circuit comprising a container in the form of a substantially continuous metallic surface, a lumped capacitor within said surface, and a pair o-f inductance elements in the form of linear conductors devoid of concentrated reactance directly connecting saidr capacitor to said surface, and a lead within said container connected to the outer surface of each of said support rods between the ends thereof and extending externally of and through said container.

l0. A highV frequency tuned oscillatory circuit comprising a container in the form of a substantially continuous metallic surface, a lumped capacitor within said surface, a pair of inductance elements in the form of linear conductors devoid of concentrated reactance directly connecting said capacitor to said surface, and a lead conductively coupled to the outer surface of each of said inductance elements extending from within said container externally of said osstraight line, and leads conductively coupled toV the outer'surface of said support rodsand extending externally of said surface Yat substantially a right angle to said support rods.

12. A. high frequency tuned oscillatory circuit comprising a substantially continuous metallic surface enclosing an inductance in the form of two metallic rods, and a capacitor in the form of a pair of separated metallic plates, one end of each rod electrically terminating at one of the plates and the other end at the enclosing surface, means for adjustingthe length of Vone of said rods within said surface for varying the distance between said plates, and leads adjustable over the lengths of said rods and extending'therefrom externally of said metallicsurface.

BRQWDER J. THOMPSON. 

